Influence of CBN grinding on the fatigue strength in a nickel-base superalloy

In this study, rotating bending fatigue tests were carried out for a nickel-base superalloy at room and elevated temperatures in order to investigate the influence of CBN (Cubic Boron Nitride) grinding on the fatigue strength. The results were discussed from the viewpoints of surface roughness, residual stress and work hardening or softening due to the CBN grinding and oxides formed at elevated temperature. The fatigue strength was increased considerably at room temperature because the crack propagation was effectively suppressed by the compressive residual stress generated in the CBN grinding process. However, this marked increase of the fatigue strength tended to disappear at elevated temperature owing to the decreases of both the compressive residual stress and the resistance to crack propagation.